This data enables Facebook not only to keep track of active users across its multiple products, but also to fill in the missing links. If three people named Smith all upload contact info for the same fourth Smith, chances are this person is related. Facebook now knows that person exists, even if he or she has never been on Facebook. And of course, people without Facebook accounts certainly can’t see what information the company has in these so-called shadow profiles.
What Mark Zuckerberg Didn’t Say About What Facebook Knows About You
Facebook has a lot more data about us than it lets on—and its tools for providing ‘complete control’ don’t do enough
When you request and download your data from Facebook—a feature Mr. Zuckerberg repeatedly referred to in answers to questions about control—this stored browsing history isn’t there.
That is reasonable, says Antonio Garcia-Martinez, a former Facebook ad-targeting product manager and current Facebook gadfly. Facebook targets ads based on an abstraction derived from your browsing history——an abstraction such as your interest in golf. When you download your data, Facebook tells you what it thinks your interests are but doesn’t provide the specific evidence for why it thinks that.
“If you downloaded this file [of sites Facebook knows you visited], it would look like a quarter to half your browsing history,” Mr. Garcia-Martinez adds.
Another reason Facebook doesn’t give you this data: The company claims recovering it from its databases is difficult. In one case, it took Facebook 106 days to deliver to a Belgian mathematician, Paul-Olivier Dehaye, all the data the company had gathered on him through its most common tracking system. Facebook doesn’t say how long it stores this information.
When you opt out of interest-based ads, the system that uses your browsing history to target you, Facebook continues tracking you anyway. It just no longer uses the data to show you ads.
There is more data Facebook collects that it doesn’t explain. It encourages users to upload their phone contacts, including names, phone numbers and email addresses. Facebook never discloses if such personal information about you has been uploaded by other users from their contact lists, how many times that might have happened or who might have uploaded it.
.. There’s also a form of location data you can’t control unless you delete your whole account. This isn’t the app’s easy-to-turn-off GPS tracking. It’s the string of IP addresses, a form of device identification on the internet, that can show where your computer or phone is each time it connects to Facebook.
Location is a powerful signal for Facebook, allowing it to infer how you are connected to other people, even if you don’t identify them as family members, co-workers or lovers.
.. All this data, plus the elements Facebook lets you control, can potentially reveal everything from your wealth to whether you are depressed.
Facebook, Alphabet Inc.’s Google and a host of smaller companies that compete with and support the giants in the digital ad space have become addicted to the kind of information that helps microtarget ads.